Highly photosensitive titanium dioxide and process for forming the same

Abstract

A high photosensitivity titanium oxide composition includes a plurality of nanosize particles including titanium dioxide and titanium suboxide. The particles are substantially non-stoichiometric (TiO 2-x , wherein 0.1<×<0.3 at a surface of the particles, and in the bulk of the particles x is less than at the surface), having a magnetic susceptibility value (χ) of at least 0.8·10 −6 cm 3 /g at 300 K and being at least 30% by weight rutile. A related method of forming a high photosensitivity titanium oxide composition includes the steps of providing a titanium chloride compound, such as titanium tetrachloride, an oxygen-containing gas and hydrogen, wherein a concentration of the hydrogen is in a stoichiometric excess (H 2 :O 2 ) from 2.02:1 to 2.61:1. The titanium chloride compound is burned in the presence of oxygen from the oxygen-containing gas and hydrogen to form plurality of ultrafine particles comprising titanium dioxide and titanium suboxide. The method can include the steps prior to the burning step of mixing the titanium chloride compound, oxygen and hydrogen and heating the same to 50 to 100° C., such as from 70-100° C.

1. A method of forming a high photosensitivity titanium oxide composition, comprising the steps of:
 providing a titanium chloride comprising compound, an oxygen (O 2 )-containing gas and hydrogen (H 2 ), wherein a molar ratio of said hydrogen with respect to oxygen from said oxygen-containing gas (H 2 :O 2 ) is from 2.02:1 to 2.61:1, and 
 burning said titanium chloride comprising compound in the presence of said (O 2 ) and said hydrogen (H 2 ) to result in a chemical reaction to form a plurality of ultrafine titanium dioxide and titanium suboxide particles, wherein essentially all of said hydrogen (H 2 ) that reacts during said method participates in said chemical reaction. 
 
     
     
       2. The method of  claim 1 , wherein said oxygen (O 2 )-containing gas is preliminarily dried, further comprising the steps prior to said burning step of mixing said titanium chloride comprising compound, said oxygen (O 2 ) and said hydrogen (H 2 ) and heating said titanium chloride comprising compound, said oxygen (O 2 ) and said hydrogen (H 2 ) to a temperature from 50 to 100° C. 
     
     
       3. The method of  claim 2 , wherein said temperature for said heating step is from 70-100° C. 
     
     
       4. The method of  claim 1 , wherein a steady state temperature during said burning step is from 700 to 1100° C. 
     
     
       5. The method of  claim 1 , further comprising the step of steaming said particles at 150-220° C. to promote desorption of HCl and Cl 2  from the surface of said particles. 
     
     
       6. The method of  claim 5 , wherein a temperature of said steaming is from 170-200° C. 
     
     
       7. The method of  claim 1 , wherein a molar ratio of said titanium chloride comprising compound to said hydrogen (H 2 ) is in a range from 1:4 to 1:2. 
     
     
       8. The method of  claim 1  wherein said titanium chloride comprising compound comprises titanium tetrachloride. 
     
     
       9. The method of  claim 1 , wherein a photocatalytic activity of said particles is 1.4-3.0 mg/ml·min·m 2  as measured in a reaction of methylene blue reduction at room temperature. 
     
     
       10. The method of  claim 1 , wherein said composition comprises a mixture of separated particles consisting essentially of said titanium dioxide and titanium suboxide particles. 
     
     
       11. The method of  claim 10 , wherein said composition includes <0.1 wt % silica.